A retrospective analysis was conducted on patients diagnosed with and treated for keratocystic odontogenic tumor (KCOT) at Mashhad School of Dentistry between 1996 and 2006. The patients comprised 44 men and 30 women with a mean age of 27.08 years. Among the total of 83 lesions, 56 (67.5%) occurred in the mandible and 27 (32.5%) in the maxilla. Swelling tended to be the most common complaint (45.8%), while 24.1% of the lesions were diagnosed incidentally. Six patients (8.1%) with a total of 15 lesions had nevoid basal cell carcinoma syndrome; 28 lesions (33.7%) were associated with an impacted tooth, and 12 (14.5%) presented daughter cysts. Sixty-six KCOTs were treated by enucleation [5 recurrences (7.6%)], 6 by marsupialization [2 recurrences (33.3%)] and 11 by marsupialization followed by enucleation (no recurrences). KCOTs in the mandible showed a higher recurrence rate than those in the maxilla (10.7% vs 3.7%). Although the demographics of Iranian patients are closely similar to those of other nationalities, in this series KCOTs tended to develop in younger patients with a peak in teenagers. The posterior region of the mandible showed the highest likelihood of KCOT occurrence and recurrence. Marsupialization followed by enucleation resulted in the lowest recurrence rate. (J. Oral Sci. 49, 229-235, 2007)